Applicator for chromatography and electrophoresis



Feb. 17, 1970 "0.1:. WILLIAMSON I ,4

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DONALD E. WILLIAMSON ATTORNEYS United States Patent 3,495,446 APPLICATOR FOR CHROMATOGRAPHY AND ELECTROPHORESIS Donald E. Williamson, Miami, Fla., assignor to Cordis Corporation, Miami, Fla., a corporation of Florida Filed June 19, 1967, Ser. No. 646,872 Int. Cl. G01n 1/28 US. Cl. 73-61.1 4 Claims ABSTRACT OF THE DISCLOSURE A chromatographic applicator for depositing a predetermined amount of fluid in a thin line on a receptive surface for subsequent analysis by chromatography or electrophoresis is described. The applicator comprises a relatively thin applicator bar having a number of discretely spaced triangular notches cut into its bottom face, each notch extending downwardly from a side face. In the preferred embodiment, alternate notches open on opposite side faces. The applicator bar may have a number of transverse break lines extending transversely to the bottom face so that smaller bars may be broken off.

BACKGROUND OF THE INVENTION Chromatographic and electrophoretic methods are frequently used to separate the components of a multi-component solution. Such methods utilize the different ionic, solubility or adsorption characteristics of the various molecular components of the solution with respect to the chromatographic material on which they are deposited.

One very simple but popular method of chromatography, known as paper chromatography, requires that the solution to be analyzed be placed on chromatographic paper in a thin line and in a precisely controlled and evenly distributed amount. The fluid is then caused to migrate along the paper and the various components are separated into zones according to the different rates at which they travel. These differing migration rates are dependent upon the physical properties of the adsorbent (i.e. paper), the properties of the molecules to be separated and the properties of the solvents used. The principles described are also applied to thin layer chromatography. A layer of the absorbent (i.e., silica gel, cellulose) is spread on a support of glass or plastic.

In using the technique of preparative chromatography, it is important to apply the fluid to the paper or layer in a uniform, thin, straight, transverse line. Heretofore, this has been done with a syringe like applicator which has the disadvantages of tearing the paper or breaking the thin layer, causing non-uniform delivery, and requiring extensive cleaning between use as well as extremely elaborate motor driven drive units, both for delivery of the sample and movement of the syringe laterally. Precise control of thickness of paper on the layer is essential. Another technique utilizes a pair of parallel wires to pickup the fluid, to apply the entire line instantaneously, but that has the disadvantage of being position sensitive. If the wires are not horizontal, fluid will drain to one end or another.

SUMMARY OF THE INVENTION I have found that an improved applicator which is capable of applying a precisely controlled quantity of fluid in a thin line on a chromatographic paper or thin layer adsorbent may be formed from a relatively thin applicator bar having a number of discretely spaced triangular notches formed in its bottom face. Preferably, alternate notches open onto opposite flat faces of the applicator bar. Fluid is retained in these notches by capillary action when the applicator bar is dipped into the solution to be analyzed. The solution is deposited on the chromatographic paper or thin layer adsorbent in a fine line of controlled thickness merely by touching the applicator to the paper or adsorbent. Break lines extending transversely to the row of notches are provided on the applicator to permit smaller applicator segments of predetermined capacity to be formed from larger applicator bars by separating bars of desired length along the appropriate lines.

Accordingly, it is an object of my invention to provide an improved applicator of relatively simple construction which is capable of depositing a precisely controlled amount of fluid on a surface.

A further object of my invention is to provide an improved applicator which is readily separable into smaller applicator segments for the application of discrete, precisely controlled quantities of fluid to a surface.

The above and other objects and advantages of my invention will be more readily understood when considered in connection with the following detailed description of a preferred embodiment of my invention which is shown in the accompanying drawings, in which:

FIG. 1 is a pictorial view of a multi-section applicator constructed in accordance with my invention;

FIG. 2 is a pictorial view of an applicator with one section broken away;

FIG. 3 is a plan view of a portion of an applicator bar;

FIG. 4 is a side sectional view of the lower portion of an applicator .bar showing the angulation of the notches; and

FIG. 5 is a bottom view of an applicator showing the arrangement of the notches in more detail.

Considering the drawings in detail, FIGS. 1 and 2 are pictorial views of an applicator bar 10 having side faces 12 and 14 sloping toward a thin bottom face 16 in which triangular notches 18 are formed; these notches extend through both the side and bottom faces of the applicator bar. Break lines 20 are formed at convenient, e.g. 2 inch intervals along the applicator bar, these lines extending transversely to the bottom face of the bar to allow the bar to be readily broken into a number of smaller applicator segments, each of which is capable of supplying a predetermined quantity of fluid to a chromatographic surface. The applicator may be formed from a number of different materials; in practice, a plastic polystyrene has been found to work well.

FIG. 3 is an enlarged plan view of a portion of the applicator bar of FIGS. 1 and 2 showing the positioning of the notches in greater detail, while FIG. 4 is a side sectional view along the line 44 of FIG. 3. As may be seen from these drawings, the notches 18 open onto both the side faces 12 and 14 and the bottom face 16 of the applicator bar, alternate notches opening onto alternate side faces of the bar. Staggering the notches in this fashion provides greater structural strength in the applicator and allows the notches to be spaced closely together while insuring that the fluid in a given notch does not come into contact with, or interfere with, the fluid in adjacent notches. Each notch thus holds a like quantity of fluid, without communicating with adjacent notches. There is therefore no possibility that fluid will run to one end or another if the applicator is tipped from the horizontal.

FIG. 4 shows the shape of each of these notches in greater detail. Starting from one of the side faces of the applicator, the notches 18 slope downwardly and toward the opposite side face to form a triangular notch a shown in FIG. 4. Fluid 22 which is brought into contact with the bottom face of the applicator adheres to the walls of the notches through capillary attraction and assumes a shape similar to that shown in FIG. 4. This fluid may be deposited on a chromatographic surface 24 by pressing the applicator against the chromatographic material to form a fine straight line having a precisely controlled quantity of fluid.

The amount of fluid deposited will, of course, depend upon the exact dimensions of the notches 18 and their spacing with respect to one another. A convenient applicator having a capacity of 50 micro-liters may be formed from an applicator bar approximately 4 inches long by 1 /2 inches high with notches Whose dimensions are those of a triangle having a base of .048 inch, a height of .0831 inch, a thickness of .0141 inch, and a pitch along the bottom face of the applicator of .0305 inch.

FIG. 5 is a bottom view of the applicator of my invention showing the arrangement of the notches in more detail. As may be seen from this figure, alternate notches open onto opposite side faces of the applicator bar. The notches extend across substantially the entire width of the bottom face of the bar and are equally spaced and distributed along the length of this face.

From the above description it may be seen that I have provided a simple, inexpensive, and efiicient fluid applica-' tor for chromatography. A precise amount of fluid may readily be deposited with the applicator of my invention and smaller amounts of fluid may readily be metered by the applicator by dividing it into smaller segments by means of pressure exerted on one or more of the break lines.

Having described a preferred embodiment of my invention, what I claim is new and desire to secure by Letters Patent is:

1. An applicator for depositing a predetermined amount of fluid on a receptive surface, comprising an applicator bar having side and bottom faces, and having a plurality of transversely extending adjacent, closelyspaced notches formed in said bar each communicating with said bottom face and with a side face, said notches being separate from each other and each being capable of holding a predetermined quantity of fluid by capillary adhesion, whereby the fluid held by the notches is not free to flow from one notch to another and said applicator may deposit said fluid uniformly on and across a receptive surface on being brought into contact therewith.

2. The applicator defined by claim 1 in which said notches are triangular and open into the bottom and side face of the bar.

3. The applicator defined in claim 2 in which said notches are positioned longitudinally along the bottom face of said bar and open onto both the bottom face and one of the side faces of said bar, alternate notche communicating with alternate faces of said applicator bar.

4. The applicator defined in claim 3 in which said applicator bar has a plurality of break lines formed at predetermined intervals and extending transversely to said bottom face whereby applicators of smaller capacity may be formed from a given applicator bar by segmenting said bar along a break line.

References Cited UNITED STATES PATENTS 3,358,496 12/1967 Farmer 73-6l.1

FOREIGN PATENTS 1,180,166 10/ 1964- Germany.

LOUIS R. PRINCE, Primary Examiner JOSEPH W. ROSKOS, Assistant Examiner 

